Raise The Roof: Green Roofing Materials

Investing in a new roof? Let us help you find the best material for your home, climate and budget.

By Jim Hackler

| July/August 2008

Durable metal shingles such as these Stone Crest Slate ones from MetalWorks are recyclable and resist rotting, cracking and breaking.

More than 11 million tons of America’s most common roofing material—asphalt shingles with an underlying fiberglass layer—end up in landfills each year when they are stripped to make room for the replacements. While asphalt shingles can be recycled into roadbed material, only a small percentage of them actually are.

Some conventional fiberglass shingles incorporate waste paper and reclaimed wood fiber in the manufacturing process. But from an eco-friendly standpoint, the new cutting-edge options, as well as a few old-fashioned favorites, are even better.

Wood

Wood shakes are split by hand for a rougher look, while wood shingles are machine sawn. Untreated, they weather to silver or gray, and most come from old-growth Western red cedar. You can, however, find them made from sustainably grown Eastern white cedar; look for products certified by the Forest Stewardship Council (with the FSC symbol).

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Wood roofing can burn easily, so it should never be installed in fire-prone areas and may make your home ineligible for home- owner’s insurance policy coverage. Some wood roofing materials come pretreated with fire-resistant chemicals; manufacturers are searching for greener ways to reduce fire hazards. Mildew, moss and lichens also can grow on wood, causing decay and making them less suitable for constantly humid climates where regular, professional cleaning is necessary. Avoid shingles treated with preservatives—especially copper chromium arsenate (CCA), a known carcinogen—which can leach into runoff.

Clay tile (also known as terra cotta) roofs have gained popularity outside their native Southwest and Florida. Made from natural materials, clay tile roofs won’t combust, decay or corrode, and they require little maintenance. Clay tiles are extremely durable; they have lasted for hundreds of years on buildings in Europe and Latin America. They have a few environmental drawbacks, however. Kiln firing requires large amounts of energy, and most homeowners will have to reinforce their home’s framing to support the weight of a clay tile roof. On the plus side, should you ever decide on a different roof, the clay can be recycled or reclaimed.

Slate

Slate tiles share many qualities with clay tiles: They have been used for centuries and are highly durable, but they are heavy and have high embodied energy because of the quarrying required to obtain granite. They are also generally quite expensive. Slate tiles are among the most easily salvaged roofing materials; a number of small companies specialize in the sales and installation of reclaimed tiles (although the price is about the same).

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Recycled rubber and plastic

Homeowners who want the look of slate without the high expense might opt for recycled rubber or plastic shingles, often referred to as polymers. “Some of the new synthetic tiles are made from old rubber tires,” says Mike Barcik, senior research engineer at Southface, an environmental education and outreach nonprofit. “From a 10-foot distance, you can’t tell they’re not real slate. They’re incredibly durable and weigh significantly less than slate.” Some rubber tiles are designed to mimic cedar shakes, at about the same price as the real thing. Rubber and plastic provide good sound insulation and are more resistant to hail and wind than wood.
Concrete and fiber-cement

Concrete tiles look and feel like clay but break less easily during installation and can be walked upon without damage. Fiber-cement is a durable alternative to wood, asphalt and even slate, and it doesn’t have slate’s excessive weight. Both concrete and fiber-cement are highly fire-resistant, but they’re both made from Portland cement, which requires a huge amount of energy to produce. Some fiber-cement options incorporate recycled content such as newspaper, which increases the environmental benefits.

Metal

Metal roofing is made from steel or aluminum and is available as shingles or standing-seam panels. Metal shingles mimic clay tiles or slate shakes in appearance, but they are far less expensive and much lighter in weight. Standing-seam metal roofs are installed as panels, which are either preformed or fabricated on site. Attached by clips that allow the metal to expand and contract during hot and cold weather, they’re one of the best rooftop options if you’re considering rainwater collection; asphalt or composite shingles can leach toxic materials.

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While metal roofs require significant amounts of energy to produce, they may also be manufactured with recycled metal content. Additionally, the roof can be recycled at the end of its life. A study by Florida Power & Light Company found that a galvanized metal roof painted white reflected enough of the sun’s rays to save 23 percent annually in cooling costs. “The greenest option is to install an Energy Star–qualified metal roof product,” says Brett Dillon, vice president of Builders Energy Rater, a Schertz, Texas, company that provides Energy Star home-certification services. Though metal roofs have a higher initial cost, they last more than twice as long as asphalt shingles, he says. Energy Star metal roofs can qualify for federal tax credits for 10 percent of the cost, up to $500.

Roofing Material Comparison

Cost

Life Expectancy (Years)

Pros

Cons

Asphalt

$

20 to 30

■ Installers easy to find
■ Recyclable material

■ Petroleum-based product
■ Generally not heat-reflective
■ Most end up in landfills

There’s always the possibility of making all or part of your roof a “green” or “living” roof, planted with vegetation. Popular in Europe but not yet in the United States, a number of different green roof systems are available to suit varying needs.

On the most basic level, all green roofs require several things, according to industry association Green Roofs for Healthy Cities (www.GreenRoofs.org): a high-quality waterproofing system that also repels invasive roots; an adequate drainage system; a filter cloth; a lightweight soil; and, of course, plants. Among many benefits, green roofs can extend the lifespan of the roofing material, reduce heating and cooling costs and stormwater runoff, and provide noise absorption and a place to garden. If whole cities had green roofs, the heat island effect—warmer urban temperatures—could be mitigated.

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